doc: reword warnings about sockets passed to subprocesses

Make the docs more concise. Make warnings direct ("do not use" and
"should") rather than "is not recommended" or "is recommended".

Backport-PR-URL: https://github.com/nodejs/node/pull/34377
PR-URL: https://github.com/nodejs/node/pull/34273


Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>